U.S. Pat. No. 6,534,970 B1 discloses a rotary position detector containing a scale unit that is arranged around the rotation axis. The measuring direction of such a rotary position detector is a circular part around the rotation axis. A scale unit contains groups of scale loops wherein these groups are distributed along the circular measuring path. Each group contains an outer loop that surrounds at least one inner loop. Each loop is formed by a conductor having two radial conductor sections that thus extend perpendicular to the measurement direction and two circumferential conductor sections that extend parallel to the measurement direction around the rotation axis. Such nested loop structures shall be less sensitive to misalignment between the scale unit and a sensor unit that moves along the circular measurement path.
U.S. Pat. No. 7,705,585 B2 discloses a detector for measuring relative position in a linear measuring direction. It contains a scale unit and a sensor unit that is movable with regard to the scale unit in the measuring direction. The sensor unit contains an antenna comprising a transmit coil and two receive coils that are displaced in the measuring direction. Each receive coil has two loops that are arranged next to each other in a transverse or height direction perpendicular to the measuring direction. One loop of each receive coil is positioned above the scale unit and the other loop is positioned distant to the scale unit. Accordingly, the magnetic field created by the transmit coil is modified in the range of one loop of each receive coil, whereas the flux through the respective other loop corresponds mainly to the far field. In so doing any disturbance due to a magnetic far field that might be present, is eliminated. The receive signal detected by means of the receive coils thus only depends on the coupling between the transmit coil, the scale unit and the receive coil. Each loop of the receive coils has a rectangular shape. The field elements arranged along the measuring direction at the scale unit can have different shapes like rhombuses, circuits or polygons.